This invention is generally in the field of fabrication processes for making structures having features of complex shapes and patterns in small feature sizes.
The field of nanotechnology has led to various fabrication methods to produce miniature-sized features. Examples of the prominent nanotechnologies include microphotonics, electronics, and MEMS, and nanomechanics. In all of these technologies, producing materials with small feature sizes typically are critical to the successful implementation of an intended product.
For example, photonic crystals (“PCs”) are a new class of optical devices for microscopic confinement and manipulation of electromagnetic radiation. Periodic dielectric crystals can exhibit bandgaps that prohibit the propagation of a certain set of frequencies of light in a manner analogous to electronic bandgaps in semiconductors. The limitation and difficulty of implementing this technology lies, for example, in the fabrication of small size features in complex three dimensional (“3D”) patterns, such as to make 3D PCs suitable for operating at visible and infrared wavelengths.
Current 3D fabrication technologies include (i) lithographic techniques where 3D structures are built up of successive two dimensional (“2D”) structures, (ii) self-assembly techniques where colloids, surfactants, zeolites, or block copolymers have been formed into desired structures and, in some cases, one component etched out and the resulting empty space backfilled with a different (high index) component, and (iii) a holographic process where the structures are built through polymerization of a monomer at specific interference patterns. These techniques, however, have various limitations. Lithographic processes are inherently a 2D process, and the fabrication of 3D structures via lithography involves painstaking efforts. Self-assembly techniques are limited to certain structures that are energetically favorable and by the inherent size scale of the self-assembling moieties. Holographic processes possess an upper limit to the maximum size features that can be obtained due to the utilization of interference of laser beams of particular wavelengths λ and available photoresists for λ.
It would be desirable to provide fabrication methods for making complicated 3D structures from a variety of materials having complex smaller scale size features, for example with periodic spacings of well-defined, micron and sub-micron scale sizes. It would also be desirable, for example, to provide a fabrication process in which a larger template structure is made by a relatively simple, conventional technique, such as 3D printing, and then replicate the structure at arbitrarily smaller size scales.